Continuous leaching process for zinc hydrometallurgy

Abstract

The invention discloses a zinc hydrometallurgy continuous leaching process, and belongs to the technical field of comprehensive utilization of solid waste resources, the leaching process comprises the following steps: 1, ball-milling slurrying: using a solution containing ammonium chloride as a slurrying agent, and carrying out ball-milling slurrying on zinc calcine to obtain slurry; 2, continuous leaching is conducted, specifically, a solution containing ammonium chloride serves as a leaching agent, the slurry is subjected to primary leaching, primary filter residues are subjected to secondary leaching after solid-liquid separation, the primary leaching time ranges from 2.5 h to 3 h, and the secondary leaching time ranges from 2 h to 2.5 h; the content of Zn in the leachate is controlled to be 40-45 g / L; the content of ammonium chloride in the solution containing ammonium chloride is 250-260 g / L. The leaching rate of zinc in the zinc calcine is improved by controlling the leaching conditions, sulfuric acid and other high-corrosivity acids are not used in the leaching process, corrosivity to equipment is small, the operation conditions are mild, on the premise that the leaching rate is guaranteed, wastewater treatment and other post-treatment are simpler, and the requirement for environmental protection is met.

Description

Technical Field

[0001] The present invention belongs to the technical field of comprehensive utilization of solid waste resources, and particularly relates to a continuous leaching process for hydrometallurgical zinc smelting. Background Art

[0002] Zinc is an important non-ferrous metal raw material. At present, most zinc is produced by hydrometallurgy. Now, zinc smelting enterprises often have two production lines, which use zinc sulfide concentrate and roasted ore leaching residue as raw materials respectively. Zinc sulfide concentrate is processed through oxidation roasting - leaching - neutralization for iron removal - purification - electrowinning process to produce zinc, and roasted ore leaching residue is processed through reduction roasting leaching - neutralization for iron removal - purification - electrowinning process to produce zinc. Zinc ferrite is easily generated during the oxidation roasting of zinc sulfide concentrate, which affects zinc leaching. In the hydrometallurgical zinc smelting process, zinc roasted ore needs to be leached. During the leaching process, due to factors such as fluctuations in the particle size of zinc roasted ore and unstable process control, the zinc content in the leaching residue is relatively high.

[0003] The patent application with the publication number CN 117625956 A discloses a method for efficiently extracting zinc from zinc roasted ore. This method includes 7 processes: neutral leaching, hot acid leaching, washing, pre-neutralization, vanadium precipitation, purification for impurity removal, electrowinning, and casting; in the neutral leaching of zinc roasted ore, the main phase ZnO is leached, realizing the efficient separation of the main element Zn and impurity elements. The supernatant I is directly electrolyzed after purification without vanadium precipitation, reducing the loss of zinc due to wrapping and inclusion during the vanadium precipitation stage; hot acid leaching of the underflow I is used to simultaneously leach ZnS, ZnFe2O4, Zn2SiO4, and impurities Pb, Fe, and Si. The leaching solution II of the roasted ore is pre-neutralized and then impurity removal is carried out by alkaline vanadium precipitation, which can effectively save alkali agents and increase the iron content in the vanadium slag compared with direct vanadium precipitation. At the same time, the combination of neutral leaching at a high liquid - solid ratio and high - acid leaching at a low liquid - solid ratio can improve the zinc leaching rate while efficiently separating zinc and impurities, and thus reduce the amount of zinc powder in the purification section. However, a large amount of acidic wastewater is generated during the sulfuric acid leaching process in this application, which contains unreacted sulfuric acid and heavy metal ions (such as zinc, iron, etc.) dissolved from zinc roasted ore. If it is directly discharged without proper treatment, it will cause serious pollution to water bodies and damage the ecological environment. Summary of the Invention

[0004] The purpose of the present invention is to provide a continuous leaching process for hydrometallurgical zinc smelting to solve the problem of low leaching efficiency of zinc roasted ore in hydrometallurgical zinc smelting.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] A continuous leaching process for hydrometallurgical zinc smelting includes the following steps:

[0007] First step, ball milling and pulping: Using a solution containing ammonium chloride as a pulping agent, zinc roasted ore is ball milled and pulped to obtain a slurry.

[0008] Step 2: Continuous leaching: Using a solution containing ammonium chloride as the leaching agent, the slurry is leached for the first time. After solid-liquid separation, the first filter residue is then leached for the second time. The first leaching time is 2.5 - 3 h, and the second leaching time is 2 - 2.5 h. Control the Zn content in the leachate to be 40 - 45 g / L. The ammonium chloride content in the solution containing ammonium chloride is 250 - 260 g / L.

[0009] In some possible implementation manners, the pH value in the continuous leaching section is adjusted to 5.0 - 5.5 with hydrochloric acid.

[0010] In some possible implementation manners, the first leaching slurry and the leaching agent are leached at a solid-liquid ratio of 1 - 1.5:10 - 15.

[0011] Basic principle: Zinc calcine reacts with ammonium chloride to form a zinc-ammonium complex, and other trace impurities (such as lead, copper, cadmium, thallium, etc.) in the raw material also undergo similar reactions.

[0012] The main chemical reactions in the leaching section are as follows:

[0013] ZnO + 2NH4Cl = Zn(NH3)2Cl2 + H2O

[0014] MeO + 2NH4Cl = Me(NH3)2Cl2 + H2O

[0015] CaO + 2NH4Cl = CaCl2 + 2NH3 + H2O

[0016] In the formula, Me is other trace impurities; the pH of the slurry in the leaching section is 5 - 6, showing weak acidity. Therefore, the NH3 generated in the leaching section will not overflow.

[0017] In some possible implementation manners, the solution containing ammonium chloride includes an ammonium chloride aqueous solution and electrolysis tail liquor. The ammonium chloride content in the electrolysis tail liquor is 250 - 260 g / L, the zinc content is 20 - 30 g / L, the iron content is 0.001 - 0.002 g / L, and the lead content is 0.002 - 0.003 g / L.

[0018] In some possible implementation manners, the zinc calcine is obtained by oxidizing roasting secondary zinc oxide and zinc-containing waste residue or is a commercially available zinc calcine for hydrometallurgical zinc smelting.

[0019] In some possible implementation manners, the zinc calcine is prepared through the following steps:

[0020] The secondary zinc oxide and zinc-containing waste residues are put into a rotary kiln for oxidative roasting. The temperature range of the kiln tail in the rotary kiln is 300 - 800 °C, which is called the preheating zone with a length of 10 - 15 m; the temperature range of the kiln head is 800 - 1500 °C, which is called the reaction zone with a length of 15 - 20 m. The raw materials of secondary zinc oxide and zinc-containing waste residues form a material flow and move from the kiln tail to the kiln head as the rotary kiln rotates, and the prepared zinc calcine is discharged from the kiln head.

[0021] In some possible implementation manners, the mass fraction of zinc in the secondary zinc oxide is 45% - 65%, and the mass fraction of zinc in the zinc-containing waste residues is 30% - 45%; the mass ratio of the secondary zinc oxide to the zinc-containing waste residues is 1 - 2:1.

[0022] In some possible implementation manners, during the oxidative roasting process, natural gas is injected into the rotary kiln through the burner spray gun at the kiln head of the rotary kiln and burns to provide heat.

[0023] In the preheating zone, at the beginning, the materials form lumps due to high humidity and form large particles. During the movement towards the kiln head, they are gradually dehydrated by heat and preheated to about 800 °C. When the materials reach the reaction zone with a temperature of 800 - 1500 °C, the chlorides and fluorides in the materials volatilize and enter the sedimentation chamber - spray tower with the rotary kiln flue gas for collection; the materials after removing chlorine and fluorine enter the cooling system from the kiln head discharge port, and after cooling, they are ball milled and packaged. The chlorine and fluorine elements in the raw materials will volatilize into the soot in the form of metal chlorides and fluorides. The rotary kiln flue gas is naturally settled and sprayed in two stages, and then purified by an alkali liquor absorption tower and an electric demister before being discharged. The zinc calcine is discharged from the kiln head, naturally cooled and then packaged and sent to the product warehouse. At the same time, a method for recycling and processing secondary zinc oxide and zinc-containing waste residues is provided.

[0024] In some possible implementation manners, in the second step, the leaching solution is taken to the laboratory for zinc content detection once an hour. If the Zn content in the leaching solution < 40 g / L, the slurry input amount is increased. After one hour, the leaching solution is taken for Zn content detection > 40 g / L, and the slurry input amount is stabilized; if the zinc in the leaching solution > 45 g / L, the slurry input amount is reduced.

[0025] In some possible implementation manners, the maximum feed amount of the ball milling and pulping process at one time is 4 - 6 t, the ball milling time is 1 - 1.5 h, and the solid-liquid ratio is controlled at 1:4 - 6 during the ball milling and pulping process. Wet ball milling is adopted, and it is carried out in a completely closed process. There is no waste gas generated during the process, and only dust is generated during the feeding process of powdery materials.

[0026] The beneficial effects of the present invention:

[0027] The present invention provides a continuous leaching process for zinc hydrometallurgy, which improves the leaching rate of zinc in zinc calcine by controlling the leaching conditions. In the leaching process of the present invention, sulfuric acid is not used, the corrosion of equipment is small, and the operating conditions are mild. On the premise of ensuring the leaching rate, the subsequent solid waste treatment such as wastewater treatment is simpler and meets the requirements of environmental protection.

[0028] In the continuous leaching process for zinc hydrometallurgy provided by the present invention, a solution containing ammonium chloride is selected as the leaching agent and pulping agent. This process system has a wide adaptability to raw materials and can process various types of zinc-containing raw materials, including low-grade zinc oxide ores and complex ores with more impurities. The generated wastewater is easier to treat, and ammonium chloride can also be recycled in the subsequent processing of the leaching solution, reducing the consumption and cost of the leaching agent. Moreover, through the control of conditions in the present invention, a high-concentration solution containing ammonium chloride is not required as the leaching agent and pulping agent, further reducing the complexity of the process and the difficulty of process operation, and the production equipment is also easier to maintain. Specific embodiments

[0029] In order to make the objectives, technical solutions and advantages of the present application clearer, the following describes and illustrates the present application in combination with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application. Based on the embodiments provided by the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present application.

[0030] Obviously, the following description is only some examples or embodiments of the present application. For those of ordinary skill in the art, the present application can also be applied to other similar scenarios without creative efforts. In addition, it can also be understood that although the efforts made in this development process may be complex and lengthy, for those of ordinary skill in the art related to the content disclosed in the present application, some design, manufacturing or production changes based on the technical content disclosed in the present application are only conventional technical means and should not be understood as the content disclosed in the present application being insufficient.

[0031] However, there will be cases where unnecessary detailed descriptions are omitted. For example, there are cases where the detailed descriptions of well-known matters are omitted and the repeated descriptions of actually identical structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the following description is provided for those skilled in the art to fully understand the present application and is not intended to limit the subject matter recited in the claims.

[0032] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions, and all technical features and optional technical features of the present application can be combined with each other to form new technical solutions.

[0033] In a continuous leaching process for zinc hydrometallurgy provided by the present invention, a solution containing ammonium chloride is selected as the leaching agent and slurrying agent. This process system has a wide adaptability to raw materials and can process various types of zinc-containing raw materials. It can not only process secondary zinc oxide and zinc-containing waste residues, but also process low-grade zinc oxide ores and complex ores with more impurities. The generated wastewater is easier to treat, and ammonium chloride can also be recycled in the subsequent processing of the leaching solution, reducing the consumption and cost of the leaching agent. And through the control of conditions in the present invention, a high-concentration solution containing ammonium chloride is not required as the leaching agent and slurrying agent, further reducing the complexity of the process and the difficulty of process operation, and the production equipment is also easier to maintain.

[0034] The following is a detailed description of a continuous leaching process for zinc hydrometallurgy in an embodiment of the present application.

[0035] An embodiment of the present application provides a continuous leaching process for zinc hydrometallurgy, which includes the following steps:

[0036] The first step, ball milling and slurrying: Using a solution containing ammonium chloride as the slurrying agent, zinc calcine is ball milled and slurried to obtain a slurry.

[0037] The second step, continuous leaching: Using a solution containing ammonium chloride as the leaching agent, the slurry is first leached. After solid-liquid separation, the primary filter residue is then subjected to secondary leaching. The primary leaching time is 2.5 - 3 h, and the secondary leaching time is 2 - 2.5 h; the Zn content in the leaching solution is controlled to be 40 - 45 g / L; the ammonium chloride content in the solution containing ammonium chloride is 250 - 260 g / L. Plate and frame filtration is used for solid-liquid separation in the leaching section. Zinc and trace impurities such as lead, copper, cadmium, and thallium in the raw materials also enter the liquid, while insoluble substances such as lead and indium enter the filter residue. The filtrate enters the oxidation and impurity removal section, and the primary filter residue is subjected to secondary leaching; the secondary leaching filter residue is returned to the rotary kiln as the raw material for producing zinc calcine.

[0038] In some embodiments, hydrochloric acid is used to adjust the pH value to 5.0 - 5.5 in the continuous leaching section.

[0039] In some embodiments, the primary leached slurry and the leaching agent are leached at a solid-liquid ratio of 1 - 1.5:10 - 15.

[0040] Basic principle: Zinc calcine reacts with ammonium chloride to form a zinc-ammonium complex, and other trace impurities (such as lead, copper, cadmium, and thallium) in the raw materials also undergo similar reactions.

[0041] The main chemical reactions in the leaching section are as follows:

[0042] ZnO + 2NH₄Cl = Zn(NH₃)₂Cl₂ + H₂O

[0043] MeO + 2NH₄Cl = Me(NH₃)₂Cl₂ + H₂O

[0044] CaO + 2NH₄Cl = CaCl₂ + 2NH₃ + H₂O

[0045] Where Me is other trace impurities; the pH of the slurry in the leaching section is 5 - 6, showing weak acidity, so the NH₃ generated in the leaching section will not overflow.

[0046] In some embodiments, the solution containing ammonium chloride includes an aqueous ammonium chloride solution and an electrolysis tail liquid. The content of ammonium chloride in the electrolysis tail liquid is 250 - 260 g / L, the content of zinc is 20 - 30 g / L, the content of iron is 0.001 - 0.002 g / L, and the content of lead is 0.002 - 0.003 g / L.

[0047] In some embodiments, the zinc calcine is obtained by oxidizing roasting secondary zinc oxide and zinc-containing waste residue or is a commercially available zinc calcine for hydrometallurgical zinc smelting.

[0048] In some embodiments, the zinc calcine is prepared by the following steps:

[0049] Put secondary zinc oxide with a zinc content of 45% - 65% and zinc-containing waste residue with a zinc content of 30% - 45% into a rotary kiln. Natural gas is injected into the rotary kiln through a burner spray gun from the head of the rotary kiln to burn and provide heat. The rotary kiln has an inclination angle, and the materials form a material flow with the rotation of the rotary kiln and move from the tail to the head of the kiln. According to its different functions, the rotary kiln can be roughly divided into a preheating zone and a reaction zone in the kiln. The temperature range at the tail of the kiln from 300 to 800 °C is called the preheating zone, with a length of 10 - 15 m; the temperature range at the head of the kiln from 800 to 1500 °C is called the reaction zone, with a length of 15 - 20 m. The raw materials of secondary zinc oxide and zinc-containing waste residue form a material flow with the rotation of the rotary kiln and move from the tail to the head of the kiln, and the prepared zinc calcine is discharged from the head of the kiln.

[0050] In some embodiments, the mass ratio of secondary zinc oxide to zinc-containing waste residue is 1 - 2:1.

[0051] In some embodiments, during the oxidizing roasting process, natural gas is injected into the rotary kiln through a burner spray gun from the head of the rotary kiln to burn and provide heat.

[0052] In the preheating zone, the material initially forms lumps due to high humidity, creating large particles. During the movement towards the kiln head, it is gradually dehydrated by heat and preheated to around 800°C. When the material reaches the reaction zone at a temperature of 800 - 1500°C, chlorides and fluorides in the material volatilize and enter the sedimentation chamber - spray tower with the rotary kiln flue gas for collection; the material after removing chlorine and fluorine enters the cooling system from the kiln head discharge port and is ball milled and packaged after cooling. Chlorine and fluorine elements in the raw materials will volatilize into the soot in the form of metal chlorides and fluorides. The rotary kiln flue gas is discharged after two-stage natural sedimentation, spraying, and then passing through an alkali liquor absorption tower and an electric demister for purification. Zinc calcine is discharged from the kiln head, naturally cooled, and then packaged and sent to the product warehouse. A method for the recovery and processing of secondary zinc oxide and zinc-containing waste residue is provided.

[0053] The leaching solution can be purified by oxidation to remove substances such as iron and arsenic (ozone (supplied by an ozone generator) is added to the liquid after leaching, and after reacting for 10 - 20 minutes, an appropriate amount of lime is added to maintain the liquid pH value at 5 - 6 and react for 40 - 50 minutes, and then it is pumped into a plate and frame filter press for pressure filtration separation. The filtrate enters the purification process, and the filter residue is returned to the roasting workshop as raw material to produce zinc calcine.).

[0054] After oxidation purification, zinc ammonium complex is obtained by zinc replacement method (the leaching solution after oxidation purification reacts in a purifier filled with zinc granules for about 40 minutes. After the impurities in the purified solution meet the requirements, it is transferred to the pressure filtration section for liquid-solid separation. The pure zinc filtrate is sent to the electrolysis section, and the filter residue is returned to the roasting workshop for utilization).

[0055] After purification, the zinc ammonium complex is electrolyzed (using a graphite plate as the anode and an aluminum plate as the cathode, with a current density of 200 - 450 A and a temperature of about 40°C). Zinc is recovered at the cathode, and the electrolysis tail liquid generated during the electrolysis process can be used for the ball milling and slurrying process after evaporation and concentration.

[0056] In some embodiments, the leaching solution is taken to the laboratory for zinc content detection once an hour in the second step. If the Zn content in the leaching solution < 40 g / L, the slurry input amount is increased. After one hour, the leaching solution is taken for Zn content detection > 40 g / L, and the slurry input amount is stabilized; if the zinc in the leaching solution > 45 g / L, the slurry input amount is reduced.

[0057] In some embodiments, the maximum feed amount in the ball milling and slurrying process is 4 - 6 t at a time, the ball milling time is 1 - 1.5 h, and the solid-liquid ratio is controlled at 1:4 - 6 during the ball milling and slurrying process. Wet ball milling is used, and it is carried out in a completely closed process. There is no waste gas generated during the process, and only dust is generated during the feeding process of powdery materials.

[0058] The following is illustrated with specific embodiments.

[0059] Example 1

[0060] This embodiment provides a continuous leaching process for zinc hydrometallurgy, which includes the following steps:

[0061] The first step is to prepare zinc calcine: Secondary zinc oxide with a zinc content of 50% and zinc-containing waste residue with a zinc content of 40% are put into a rotary kiln according to a mass ratio of 2:1. Natural gas is injected into the rotary kiln through the burner spray gun at the kiln head and burned to provide heat. The rotary kiln has an inclination angle, and the materials form a material flow moving from the kiln tail to the kiln head as the rotary kiln rotates. The rotary kiln can be roughly divided into a preheating zone and a reaction zone according to its different functions. The temperature range at the kiln tail of 300 - 800 °C is called the preheating zone, with a length of 15 m; the temperature range at the kiln head of 800 - 1500 °C is called the reaction zone, with a length of 20 m. The zinc calcine is discharged from the kiln head, and after natural cooling, it is packaged and sent to the product warehouse.

[0062] Ball milling and pulping: Using ammonium chloride aqueous solution with a concentration of 250 g / L as the pulping agent, the zinc calcine is ball milled and pulped to obtain a slurry; the feeding amount of the ball milling and pulping process is 6 t, the ball milling time is 1.5 h, and the solid-liquid ratio is controlled at 1:5 during the ball milling and pulping process.

[0063] The second step is continuous leaching: Using ammonium chloride aqueous solution with a concentration of 250 g / L as the leaching agent, the slurry is leached for the first time. The slurry and the leaching agent are leached according to a solid-liquid ratio of 1:10. After solid-liquid separation, the primary filter residue is leached for the second time. The first leaching time is 2.5 h, and the second leaching time is 2 h; the Zn content in the leaching solution is controlled at 40 - 45 g / L; the leaching solution is taken once an hour and sent to the laboratory for zinc content detection. If the Zn content in the leaching solution < 40 g / L, the input amount of the slurry is increased. After one hour, the leaching solution is taken for Zn content detection > 40 g / L, and the input amount of the slurry is stabilized; if the zinc in the leaching solution > 45 g / L, the input amount of the slurry is reduced.

[0064] In the continuous leaching section, hydrochloric acid is used to adjust the pH value to the range of 5.0 - 5.5. Plate and frame filtration is used for solid-liquid separation in the leaching section. Zinc and trace impurities such as lead, copper, cadmium, and thallium in the raw materials also enter the liquid, while insoluble substances such as lead and indium enter the filter residue. The filtrate enters the oxidation and impurity removal section, and the primary filter residue is leached for the second time; the second leaching filter residue is returned to the rotary kiln as the raw material for producing zinc calcine. The zinc content of the leaching residue is tested to be 15.11%.

[0065] Example 2

[0066] Compared with Example 1, the difference in this embodiment is that the concentration of the ammonium chloride aqueous solution is 255 g / L, and the rest of the raw materials and the preparation process are the same as those in Example 1. The zinc content of the leaching residue is tested to be 15.02%.

[0067] Example 3

[0068] Compared with Example 1, this example is different in that the concentration of the ammonium chloride aqueous solution is 258 g / L, and the remaining raw materials and preparation process are the same as those in Example 1. The zinc content in the leaching residue was tested to be 15.12%.

[0069] Example 4

[0070] Compared with Example 1, this example is different in that the concentration of the ammonium chloride aqueous solution is 260 g / L, and the remaining raw materials and preparation process are the same as those in Example 1. The zinc content in the leaching residue was tested to be 15.09%.

[0071] Example 5

[0072] Compared with Example 1, in this example, the ammonium chloride aqueous solution is replaced with electrolysis tail liquid. The content of ammonium chloride in the electrolysis tail liquid is 250 g / L, the content of zinc is 20 g / L, the content of iron is 0.001 g / L, and the content of lead is 0.002 g / L.

[0073] The remaining raw materials and preparation process are the same as those in Example 1. The zinc content in the leaching residue was tested to be 15.15%.

[0074] Example 6

[0075] Compared with Example 1, in this example, the ammonium chloride aqueous solution is replaced with electrolysis tail liquid. The content of ammonium chloride in the electrolysis tail liquid is 260 g / L, the content of zinc is 30 g / L, the content of iron is 0.002 g / L, and the content of lead is 0.003 g / L.

[0076] The remaining raw materials and preparation process are the same as those in Example 1. The zinc content in the leaching residue was tested to be 15.11%.

[0077] Example 7

[0078] Compared with Example 1, in this example, the primary leaching time is 2.5 h and the secondary leaching time is 2.5 h; the remaining raw materials and preparation process are the same as those in Example 1. The zinc content in the leaching residue was tested to be 15.10%.

[0079] Example 8

[0080] Compared with Example 1, in this example, the primary leaching time is 3 h and the secondary leaching time is 2 h; the remaining raw materials and preparation process are the same as those in Example 1. The zinc content in the leaching residue was tested to be 15.05%.

[0081] Comparative Example 1

[0082] Compared with Example 1, in this comparative example, the concentration of the ammonium chloride aqueous solution is adjusted to 240 g / L, and the remaining raw materials and preparation process are the same as those in Example 1. The zinc content in the leaching residue was tested to be 20.02%.

[0083] Comparative Example 2

[0084] In this comparative example, compared with Example 1, the concentration of the ammonium chloride aqueous solution was adjusted to 270 g / L, and the other raw materials and the preparation process were the same as those in Example 1. The zinc content in the leaching residue was measured to be 15.12%. Crystallization occurred, causing blockage of the pipeline and affecting normal production.

[0085] Comparative Example 3

[0086] In this comparative example, compared with Example 1, the concentration of the ammonium chloride aqueous solution was adjusted to 280 g / L, and the other raw materials and the preparation process were the same as those in Example 1. The zinc content in the leaching residue was measured to be 15.08%. Crystallization occurred, causing blockage of the pipeline and affecting normal production.

[0087] Comparative Example 4

[0088] In this comparative example, compared with Example 1, secondary leaching was not carried out:

[0089] Using an ammonium chloride aqueous solution with a concentration of 250 g / L as the leaching agent, the slurry was leached once. The slurry and the leaching agent were leached at a solid-liquid ratio of 1:10. After solid-liquid separation, the primary filter residue was then leached twice. The primary leaching time was 2.5 h, and plate-and-frame filtration was used in the leaching section for solid-liquid separation. Zinc and trace impurities such as lead, copper, cadmium, and thallium in the raw materials also entered the liquid, while insoluble substances such as lead and indium entered the filter residue. The filtrate entered the oxidation and impurity removal section. The zinc content in the residue after primary leaching was measured to be 22%.

[0090] Comparative Example 5

[0091] In this comparative example, compared with Example 1, the primary leaching time was 1 h and the secondary leaching time was 1 h; the other raw materials and the preparation process were the same as those in Example 1. The zinc content in the leaching residue was measured to be 20.07%.

[0092] Comparative Example 6

[0093] In this comparative example, compared with Example 1, the primary leaching time was 4 h and the secondary leaching time was 2 h; the other raw materials and the preparation process were the same as those in Example 1. The zinc content in the leaching residue was measured to be 15.07%

[0094] Comparative Example 7

[0095] In this comparative example, compared with Example 1, the primary leaching time was 4 h and the secondary leaching time was 3 h; the other raw materials and the preparation process were the same as those in Example 1. The zinc content in the leaching residue was measured to be 15.06%

[0096] From the results of the zinc content in the leaching residue recorded in Examples 1 - 8 and Comparative Examples 1 - 7, it can be seen that the continuous leaching process described in the present invention can improve the leaching efficiency of zinc, and no waste gas is generated during the whole process, the equipment will not be corroded, and the generated leaching residue can be reused.

[0097] From the result comparison between Example 1 and Comparative Examples 1 - 3, it can be seen that reducing the concentration of ammonium chloride in the leaching agent is not conducive to improving the leaching efficiency. However, increasing the concentration of the leaching agent makes the leaching solution prone to crystallization, causing pipeline blockage and affecting normal production.

[0098] From the result comparison between Example 1 and Comparative Example 4, it can be seen that not performing secondary leaching will not only reduce the leaching rate of zinc, but also lead to a decrease in the overall efficiency of the leaching process and fail to achieve the effect of continuous leaching.

[0099] From the result comparison between Example 1 and Comparative Examples 5 - 7, it can be seen that shortening the leaching time will reduce the leaching rate of zinc. However, extending the leaching time is also not conducive to improving production efficiency and will increase the input time cost.

[0100] It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non - exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements, but also includes other elements not expressly listed, or elements inherent to such process, method, article or device.

[0101] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A continuous leaching process for hydrometallurgical zinc smelting, characterized in that: The steps include: The first step is ball milling: using a solution containing ammonium chloride as a slurrying agent, ball milling the zinc roasted sand to obtain a slurry; The second step is continuous leaching: using a solution containing ammonium chloride as a leaching agent, the slurry is leached for the first time, and the filter residue after solid-liquid separation is leached for the second time. The first leaching time is 2.5 to 3 hours, and the second leaching time is 2 to 2.5 hours; the Zn content of the leaching solution is controlled to be 40 to 45 g / L; the content of ammonium chloride in the solution containing ammonium chloride is 250 to 260 g / L.

2. A continuous leaching process for hydrometallurgical zinc smelting according to claim 1, characterized in that: In the continuous leaching stage, the pH value is adjusted to 5.0-5.5 with hydrochloric acid.

3. A continuous leaching process for hydrometallurgical zinc smelting according to claim 1, characterized in that: During the first leaching, the slurry and the leaching agent are leached at a solid-liquid ratio of 1-1.5:10-15.

4. A continuous leaching process for hydrometallurgical zinc smelting according to claim 1, characterized in that: The solution containing ammonium chloride comprises an aqueous ammonium chloride solution and an electrolytic tail liquid, wherein the content of ammonium chloride in the electrolytic tail liquid is 250-260 g / L, the content of zinc is 20-30 g / L, the content of iron is 0.001-0.002 g / L, and the content of lead is 0.002-0.003 g / L.

5. A continuous leaching process for hydrometallurgical zinc smelting according to claim 1, characterized in that: The zinc roasted sand is obtained by oxidative roasting of zinc oxide and zinc-containing waste slag or is commercially available zinc roasted sand for hydrometallurgy of zinc.

6. A continuous leaching process for hydrometallurgical zinc smelting according to claim 1, characterized in that: The zinc roasted sand is prepared by the following steps: The secondary zinc oxide and zinc-containing waste slag are put into a rotary kiln for oxidation roasting. The temperature range of 300-800°C at the kiln tail of the rotary kiln is called the preheating zone, which has a length of 10-15m; the temperature range of 800-1500°C at the kiln head is called the reaction zone, which has a length of 15-20m. The secondary zinc oxide and zinc-containing waste slag raw materials form a flow as the rotary kiln rotates, moving from the kiln tail to the kiln head, and the prepared zinc roasted sand is discharged from the kiln head.

7. A continuous leaching process for hydrometallurgical zinc smelting according to claim 5, characterized in that: The mass fraction of zinc in the secondary zinc oxide is 45% to 65%, the mass fraction of zinc in the zinc-containing waste slag is 30% to 45%; the mass ratio of the secondary zinc oxide to the zinc-containing waste slag is 1-2:

1.

8. A continuous leaching process for hydrometallurgical zinc smelting according to claim 5, characterized in that: During the oxidation roasting process, natural gas is injected from the kiln head of the rotary kiln through the burner spray gun into the rotary kiln for combustion to provide heat.

9. A continuous leaching process for hydrometallurgical zinc smelting according to claim 1, characterized in that: In the second step, the leachate is taken once every hour and sent to the laboratory to test the zinc content. If the Zn content of the leachate is less than 40g / L, increase the amount of slurry input. After one hour, take the leachate to test the Zn content. If it is greater than 40g / L, stabilize the amount of slurry input. If the zinc content of the leachate is greater than 45g / L, reduce the amount of slurry input.

10. A continuous leaching process for hydrometallurgical zinc smelting according to claim 1, characterized in that: The maximum feed amount of the ball milling process is 4-6t, the ball milling time is 1-1.5h, and the solid-liquid ratio is controlled at 1:4-6 during the ball milling process.